diff --git a/api/index.js b/api/index.js
index adfd3317..333b62dd 100644
--- a/api/index.js
+++ b/api/index.js
@@ -8,7 +8,36 @@ import {
   renderError,
 } from "../src/common/utils.js";
 import { fetchStats } from "../src/fetchers/stats-fetcher.js";
-import { isLocaleAvailable } from "../src/translations.js";
+import { validateQueryStringParams } from "../src/common/validate.js";
+
+const QUERYSTRING_PARAMS_DATA_TYPE_MAP = new Map([
+  ["username", "string"],
+  ["hide", "enum-array"],
+  ["hide_title", "boolean"],
+  ["hide_border", "boolean"],
+  ["card_width", "number"],
+  ["hide_rank", "boolean"],
+  ["show_icons", "boolean"],
+  ["include_all_commits", "boolean"],
+  ["line_height", "number"],
+  ["title_color", "string"],
+  ["ring_color", "string"],
+  ["icon_color", "string"],
+  ["text_color", "string"],
+  ["text_bold", "boolean"],
+  ["bg_color", "string"],
+  ["theme", "enum"],
+  ["cache_seconds", "number"],
+  ["exclude_repo", "array"],
+  ["custom_title", "string"],
+  ["locale", "enum"],
+  ["disable_animations", "boolean"],
+  ["border_radius", "number"],
+  ["border_color", "string"],
+  ["number_format", "enum"],
+  ["rank_icon", "enum"],
+  ["show", "enum-array"],
+]);
 
 export default async (req, res) => {
   const {
@@ -45,11 +74,9 @@ export default async (req, res) => {
     return res.send(renderError("Something went wrong"));
   }
 
-  if (locale && !isLocaleAvailable(locale)) {
-    return res.send(renderError("Something went wrong", "Language not found"));
-  }
-
   try {
+    validateQueryStringParams(req.query, QUERYSTRING_PARAMS_DATA_TYPE_MAP);
+
     const showStats = parseArray(show);
     const stats = await fetchStats(
       username,
diff --git a/src/common/validate.js b/src/common/validate.js
new file mode 100644
index 00000000..5535eecc
--- /dev/null
+++ b/src/common/validate.js
@@ -0,0 +1,126 @@
+// @ts-check
+
+import { availableLocales } from "../translations.js";
+import { themes } from "../../themes/index.js";
+import { parseArray } from "./utils.js";
+
+/**
+ * Class for handling invalid query string param errors.
+ */
+class InvalidQueryStringParamsError extends Error {
+  /**
+   * Constructor for InvalidQueryStringParamsError.
+   *
+   * @param {string} message - The error message.
+   * @param {string} secondaryMessage - The secondary error message.
+   */
+  constructor(message, secondaryMessage) {
+    super(message);
+    this.secondaryMessage = secondaryMessage;
+  }
+}
+
+const QUERYSTRING_PARAMS_ENUM_VALUES = {
+  hide: ["stars", "commits", "prs", "issues", "contribs"],
+  theme: Object.keys(themes),
+  locale: availableLocales,
+  number_format: ["short", "long"],
+  rank_icon: ["github", "percentile", "default"],
+  show: [
+    "reviews",
+    "discussions_started",
+    "discussions_answered",
+    "prs_merged",
+    "prs_merged_percentage",
+  ],
+};
+
+/**
+ * Returns the secondary error message for an invalid query string param.
+ *
+ * @param {string} param - The invalid query string param.
+ * @param {Map<string, string>} queryStringParamsDataTypeMap - The query string params data type map.
+ * @returns {string} The secondary error message.
+ */
+const getInvalidQueryStringParamsErrorSecondaryMessage = (
+  param,
+  queryStringParamsDataTypeMap,
+) => {
+  const expectedDataType = queryStringParamsDataTypeMap.get(param);
+  if (expectedDataType === "enum" || expectedDataType === "enum-array") {
+    return `Expected: ${QUERYSTRING_PARAMS_ENUM_VALUES[param].join(", ")}`;
+  } else if (expectedDataType === "number") {
+    return "Expected: a number";
+  } else if (expectedDataType === "boolean") {
+    return "Expected: true or false";
+  } else if (expectedDataType === "array") {
+    return "Expected: an array";
+  } else if (expectedDataType === "string") {
+    return "Expected: a string";
+  } else {
+    throw new Error("Unexpected behavior");
+  }
+};
+
+/**
+ * Validates the query string params.
+ * Throws an error if a query string param is invalid.
+ * Does not return anything.
+ *
+ * @param {object} queryStringParams - The query string params.
+ * @param {Map<string, string>} queryStringParamsDataTypeMap - The query string params data type map.
+ * @returns {void}
+ */
+const validateQueryStringParams = (
+  queryStringParams,
+  queryStringParamsDataTypeMap,
+) => {
+  for (const [param, value] of Object.entries(queryStringParams)) {
+    const expectedDataType = queryStringParamsDataTypeMap.get(param);
+    if (!expectedDataType) {
+      throw new InvalidQueryStringParamsError(
+        `Invalid query string param: ${param}`,
+        "Expected: a valid query string param",
+      );
+    }
+    if (expectedDataType === "enum") {
+      if (QUERYSTRING_PARAMS_ENUM_VALUES[param].includes(value)) {
+        continue;
+      }
+    } else if (expectedDataType === "enum-array") {
+      const values = parseArray(value);
+      if (
+        values.every((value) =>
+          QUERYSTRING_PARAMS_ENUM_VALUES[param].includes(value),
+        )
+      ) {
+        continue;
+      }
+    } else if (expectedDataType === "number") {
+      if (!isNaN(value)) {
+        continue;
+      }
+    } else if (expectedDataType === "boolean") {
+      if (value === "true" || value === "false") {
+        continue;
+      }
+    } else if (expectedDataType === "array") {
+      if (Array.isArray(parseArray(value))) {
+        continue;
+      }
+    } else if (expectedDataType === "string") {
+      if (typeof value === "string") {
+        continue;
+      }
+    }
+    throw new InvalidQueryStringParamsError(
+      `Invalid query string param: ${param}`,
+      getInvalidQueryStringParamsErrorSecondaryMessage(
+        param,
+        queryStringParamsDataTypeMap,
+      ),
+    );
+  }
+};
+
+export { validateQueryStringParams };
diff --git a/tests/api.test.js b/tests/api.test.js
index a6ed04b5..2cc1854f 100644
--- a/tests/api.test.js
+++ b/tests/api.test.js
@@ -6,6 +6,7 @@ import { calculateRank } from "../src/calculateRank.js";
 import { renderStatsCard } from "../src/cards/stats-card.js";
 import { CONSTANTS, renderError } from "../src/common/utils.js";
 import { expect, it, describe, afterEach } from "@jest/globals";
+import { availableLocales } from "../src/translations.js";
 
 const stats = {
   name: "Anurag Hazra",
@@ -125,8 +126,8 @@ describe("Test /api/", () => {
       {
         username: "anuraghazra",
         hide: "issues,prs,contribs",
-        show_icons: true,
-        hide_border: true,
+        show_icons: "true",
+        hide_border: "true",
         line_height: 100,
         title_color: "fff",
         icon_color: "fff",
@@ -255,8 +256,8 @@ describe("Test /api/", () => {
       {
         username: "anuraghazra",
         hide: "issues,prs,contribs",
-        show_icons: true,
-        hide_border: true,
+        show_icons: "true",
+        hide_border: "true",
         line_height: 100,
         title_color: "fff",
         ring_color: "0000ff",
@@ -301,7 +302,10 @@ describe("Test /api/", () => {
 
     expect(res.setHeader).toBeCalledWith("Content-Type", "image/svg+xml");
     expect(res.send).toBeCalledWith(
-      renderError("Something went wrong", "Language not found"),
+      renderError(
+        "Invalid query string param: locale",
+        `Expected: ${availableLocales.join(", ")}`,
+      ),
     );
   });
 
@@ -311,7 +315,7 @@ describe("Test /api/", () => {
       .reply(200, { error: "Some test error message" });
 
     const { req, res } = faker(
-      { username: "anuraghazra", include_all_commits: true },
+      { username: "anuraghazra", include_all_commits: "true" },
       data_stats,
     );